Laboratory Studies

Recommended laboratory studies for children with fever without a focus are based on the child's appearance, age, and temperature.
[12]

Begin intravenous (IV) or intramuscular (IM) antibiotic administration for all infants who appear ill once urine and blood specimens are obtained.

Perform the following for children who do not appear toxic:

Perform
urinalysis (UA) by bladder catheterization and
urine culture based on the following criteria: all males younger than 6 months and all uncircumcised males younger than 12 months; all females younger than 24 months and older female children if symptoms suggest a urinary tract infection (UTI).

Rapid testing for viruses (eg,
influenza,
respiratory syncytial virus) may be useful to decrease the need for other studies and/or antibiotic therapy. Newer multiplex PCR-based panels are available in many ER and inpatient settings that can detect multiple viruses at once, including RSV, influenza, adenovirus, parainfluenza, metapneumovirus, and rhinovirus.

Consider obtaining stool for WBC counts and guaiac if diarrhea is present.

For unimmunized patients, consider performing a CBC and blood culture in addition to the workup above, regardless of how ill-appearing the patient is.

Consider obtaining a chest radiograph. Chest radiography should be performed for patients with a WBC count greater than 20,000/μL.

Perform UA by bladder catheterization and urine culture based on the following criteria: all males younger than 6 months and all uncircumcised males younger than 12 months; all females younger than 24 months and older female children if symptoms suggest a UTI.

Obtain
CSF and perform studies and culture. Administer antibiotics before performing the
lumbar puncture (LP) if any delay is anticipated.

A study by Martinez et al analyzed the prevalence of bacterial meningitis in infants younger than 90 days with fever without a source. The study found that lumbar puncture was performed in 639 (27.0%) of the 2362 infants with fever without a source and the rate was higher in not well appearing infants (60.9%) and in those ≤21 days old (70.1%). 9 infants ≤21 days old and 5 not well-appearing infants were diagnosed with bacterial meningitis and none of the well-appearing infants were diagnosed.
[13]

Rapid testing for viruses (eg, influenza, respiratory syncytial virus, etc.) may be useful to decrease the need for other studies and/or antibiotic therapy, as above

The role of measurement of
C-reactive protein and
procalcitonin in the evaluation of these infants is under investigation but is unclear at present.
[14, 15, 16] Some newer unpublished data recently presented at national meetings suggests a negative procalcitonin may be a useful marker for ruling out SBI but further work is needed.

Next:

Imaging Studies

Chest radiography is part of any thorough evaluation of a febrile child.
[14]

Chest radiography is indicated when the patient has tachypnea, retractions, focal auscultatory findings, or oxygen saturation level in room air of less than 95%.

Although viral etiologies are considered the cause of most pediatric pneumonias, establishing a viral or bacterial etiology may be challenging.

Mark R Schleiss, MD Minnesota American Legion and Auxiliary Heart Research Foundation Chair of Pediatrics, Professor of Pediatrics, Division Director, Division of Infectious Diseases and Immunology, Department of Pediatrics, University of Minnesota Medical School